Many different types of sofa beds have been manufactured with a bed frame for folding a mattress into a storage seat position. The sofa beds presently available usually have complicated operating mechanisms for folding and unfolding the bed sections which increases the cost of manufacture and adds to the weight and bulk of the sofa bed.
In order to provide a mattress of sufficient length to accommodate a person of average height, while maintaining the width of the seat of the sofa bed about the same as the width of a conventional normal sofa seat, many sofa beds are provided with a very thick backrest so that a portion of the bed frame and/or mattress may be stored in substantially a vertical position in the backrest. Examples of various types of sofa beds in which a portion of the bed frame and/or mattress is stored behind the backrest are disclosed in U.S. Pat. Nos. 4,227,268; 4,204,287; 4,086,671; 3,974,529; 3,934,281; and 2,007,988.
The provision of a thick backrest to provide for the storage of a portion of the bed frame and/or mattress adds to the width of the sofa bed. This additional width is objectionable because sofa beds are normally used in areas where floor space is limited. Also, the provision of a thick backrest imposes undesirable limitations on the designer of sofa beds.